Toughened thermoplastics

ABSTRACT

Functionalized thermoplastics such as styrene-maleic anhydride copolymers polystyrene or maleated polyolefins may be thoughened with halogenated rubbers which are copolymers of isoprene and isobutylene provided a dialkyl or dihydroxyalkyl amino alkanol is present as a compatibilizer. The toughened thermoplastics have about a two fold increase in IZOD impact resistance.

This is a division of application Ser. No. 340,284 filed Apr. 19, 1989,now U.S. Pat. No. 4,921,910.

FIELD OF THE INVENTION

The present invention relates to toughened thermoplastics. Moreparticularly, the present invention relates to polyolefins and styrenicpolymers which contain anhydrides of carboxylic acid which are toughenedwith an halogenated butyl rubber. The thermoplastic blend also containsa tertiary amine alcohol.

BACKGROUND OF THE INVENTION

Thermoplastics have a wide variety of uses. This is generally due totheir processing ease, making it possible to mold difficult or intricateshapes fairly easily. Unfortunately some thermoplastics tend to bebrittle. Thus, they tend to break on impact. One of the methods toimprove the toughness of thermoplastics is to incorporate therein smallamounts of a dispersed rubbery phase. This has resulted in materialssuch as high impact polystyrene (HIPS). This type of tough polymer maybe prepared by grafting a thermoplastic onto a rubbery polymer duringpolymerization of the thermoplastic. Such procedures are well known tothose skilled in the art.

It is also possible in some circumstances to physically blendthermoplastics and impact modifiers. Representative of such blending artare U.S. Pat. Nos. 4,172,859 and 4,174,358 to Epstein. However, if therubbery phase is not compatible with the thermoplastic, there will notbe an enhancement of the properties of the thermoplastic, in fact, theimpact properties may likely decrease.

It is known that tertiary amines will react with halogens to produce aquaternary amine. U.S. Pat. No. 4,355,139 issued Oct. 19, 1982 to Coranet al assigned to Monsanto discloses a compatibilizing blend of afunctionalized poly alpha olefin and an amine modified nitrile rubber.The disclosure of the Coran patent illustrates a tertiary amine linkageet Col. 3. The chlorine from the olefin reacts with an amine in thenitrile rubber. This does not suggest the butyl rubber impact modifiersof the present invention.

It is known that halobutyl rubber in admixture with amine containingcompounds has good "green" strength. This is disclosed in U.S. Pat. No.4,256,857 issued Mar. 17, 1981 to Buckler et al, assigned to PolysarLimited. The Buckler patent does not suggest that such halobutyl rubbercould be used as a toughening agent for thermoplastics.

The present invention seeks to provide novel compositions ofthermoplastics toughened with halogenated butyl rubber.

SUMMARY OF THE INVENTION

The present invention provides a polymeric blend comprising:

A) per 100 parts by weight of a polymer selected from the groupconsisting of:

i) C₂₋₃ poly alpha olefins which have been grafted with from 0.1 to 10weight percent of a C₄₋₈ anhydride of a dicarboxylic acid; and

ii) polymers comprising:

a) from 50 to 99 weight percent of one or more C₈₋₁₂ vinyl aromaticmonomers which are unsubstituted or substituted by a chlorine atom or aC₁₋₄ alkyl radical;

b) from 1 to 20 weight percent of one or more anhydrides of a C₄₋₈dicarboxylic acid; and

c) optionally up to 15 weight percent of one or more C₁₋₈ alkyl estersof a C₃₋₆ ethylenically unsaturated carboxylic acid;

B) from 20 to 80 parts by weight of a copolymer of isoprene andisobutylene in a molar ratio of 1:99 to 3:97, which polymer has beenhalogenated with from 0.5 to 3 weight percent of chlorine or bromine;and

C) from 0.5 to 1.5 parts by weight of one or more compatibilizing agentsselected from the group consisting of:

i) C₂₋₁₀ aminoalkanols which are substituted at the nitrogen atom by tworadicals selected from the group consisting of C₁₋₄ alkyl andhydroxyalkyl radicals;

ii) C₆₋₁₀ aromatic ethers of C₂₋₁₀ aminoalkanols which are substitutedat the nitrogen atom by two radicals selected from the group consistingof C₁₋₄ alkyl and hydroxyalkyl radicals;

iii) C₄₋₁₀ aminoalkenols which are substituted at the nitrogen atom bytwo radicals selected from the group consisting of C₁₋₄ alkyl andhydroxyalkyl radicals provided that the ethylenic unsaturation is notadjacent the nitrogen atom or a hydroxyl radical; and

iv) C₆₋₁₀ aromatic ethers of C₄₋₁₀ aminoalkenols which are substitutedat the nitrogen atom by two radicals selected from the group consistingof C₁₋₄ alkyl and hydroxyalkyl radicals provided that the ethylenicunsaturation is not adjacent the nitrogen atom or a hydroxyl radical.

The present invention also provides a method for preparing the abovetoughened thermoplastics which comprises high shear mixing a melt ofcomponents A as described above with a masterbatch of components B and Cas described above. Preferably, components B and C as described aboveare provided as a masterbatch and mixed under high shear with componentA.

The present invention also provides a masterbatch comprising 20 to 80parts by weight of component B as described above and 0.5 to 1.5 partsby weight of component C as described above.

DETAILED DESCRIPTION

The thermoplastic materials useful in accordance with the presentinvention are generally polyolefins or styrene based thermoplasticswhich contain an anhydride of a C₄₋₈ dicarboxylic acid.

Typically, the polyolefins are polyethylene or polypropylene which havebeen grafted with from 0.1 to 10, preferably 0.1 to 5, more preferably0.1 to 3 weight percent of maleic anhydride. The processes for suchgrafting are well known. A representative process is disclosed U.S. Pat.No. 4,147,740 issued Apr. 3, 1979 to General Electric. Preferably, thepolyolefin contains from 0.1 to 5, most preferably 0.1 to 3 weightpercent of maleic anhydride.

The styrenic type polymers comprise:

from 50 to 99 weight percent of one or more C₈₋₁₂ vinyl aromaticmonomers which are unsubstituted or substituted by a chlorine atom or aC₁₋₄ alkyl radical;

from 1 to 20 weight percent of one or more C₄₋₈ anhydrides of adicarboxylic acid and optionally up to 15 weight percent of one or moreC₁₋₈ alkyl esters of a C₃₋₆ ethylenically unsaturated carboxylic acid.

Useful vinyl aromatic monomers include styrene, alpha methyl styrene,and para methyl styrene. Useful anhydrides include maleic anhydride.Useful alkyl esters include methyl methacrylate, ethyl methacrylate,methyl acrylate ethyl acrylate, butyl methacrylate, butyl acrylate andtheir homologues of higher acids (such as itaconic and fumaric acid).

If the alkyl esters are not present in the styrenic type polymer, apreferred composition comprises from 80 to 99 weight percent of one ormore of said vinyl aromatic monomers and from 1 to 20 weight percent ofone or more of said C₄₋₈ anhydrides of a dicarboxylic acid.

If the alkyl ester is present in the styrenic type thermoplastic, apreferred composition comprises from 65 to 96 weight percent of one ormore of said vinyl aromatic monomers; from 1 to 20 weight percent of oneor more of said C₄₋₈ anhydride of a dicarboxylic acid; and from 3 to 15weight percent of one or more of said alkyl esters.

The halogenated butyl rubber (or halobutyl rubber) useful in accordancewith the present invention comprises a copolymer of isoprene andisobutylene in a molar ratio of 1:99 to 3:97. Generally, the polymerswill have a molecular weight (determined by viscosity) of from about350,000 to about 450,000. The polymer is halogenated in a hydrocarbonsolvent and may contain from 0.5 to 3 weight percent of halogen.Typically brominated butyl rubber contains from about 1.0 to 2.5 mostpreferably 1.5 to 2.2 weight percent bromine. Typically chlorinatedbutyl rubber contains from about 1.0 to about 1.5 weight percentchlorine. These polymers are commercially available and are discussed inthe literature. A useful text discussing butyl and halobutyl rubbers isRubber Technology Second Edition, edited by Maurice Morton, Van NostrandReinhold Company, 1973, New York, N.Y.

The third component in the compositions of the present invention may becharacterized as a dialkyl or dihydroxy alkyl amino alkanol. Thecompounds may be characterized by the formula: ##STR1## wherein R₁ andR₂ are C₁₋₄, preferably C₁₋₂, alkyl or hydroxy alkyl radicals.

R₃ is a C₂₋₁₀ alkanol radical or a C₄₋₁₀ hydroxy alkenyl radicalprovided the double bond is not adjacent the nitrogen atom or thehydroxyl group.

R₄ is a C₆₋₁₀ aromatic radical, preferably a phenyl radical, and n iseither 0 or 1.

Preferred tertiary amino alkanols include dimethyl aminoethanol, diethylaminoethanol, dimethyl amino propanol, diethyl aminopropanol, dimethylaminobutanol, diethyl aminobutanol, dimethyl aminopentanol, and diethylaminopentanol.

If a phenyl ether is used, preferably it has the formula: ##STR2##

There are several options in preparing the compositions of the presentinvention. The compositions may be prepared in an intensive mixer or thecompounds may be prepared in an extruder provided there is sufficienttime to permit the reactions between the anhydride of the thermoplastic,the hydroxyl group on the amine and the halide of the rubber with theamine.

In each of these options there are two further options. The ingredientsmay be fed directly to the high shear mixer or the extruder. In someinstances, however, the amine may be volatile at the melting temperatureof the thermoplastic. In these instances a master batch of rubber andamine is prepared. The master batch of rubber and amine is then fed toan intensive mixer or extruder together with the thermoplastic.

If a master batch is prepared, the halobutyl rubber and the amine areblended in a high shear mixer at a temperature up to about 90° C.,preferably from room temperature up to about 70° C. The resultingmasterbatch maybe suitably comminuted. It should be noted that themasterbatch is a butyl rubber having a high green strength.

To prepare the product of the present invention the thermoplastic, thehalobutyl rubber and the amine (or master batch) are mixed using a highshear mixer having a suitable heating means or an extruder. Plasticpolystyrene based compounds, should be heated to from about 190° to220°, preferably 200° to 220° C. For the polyolefins the temperatureshould be from 120° up to 220° C. preferably from about 200° to 220° C.

There are a number of suitable high shear mixers available with suitableheating devices including Banbury mixers, Haake mixers and Brabendermixers.

There are a number of extruders which may be used. If a single screwextruder is used, the screw may have a length to diameter ratio from12:1 to 35:1 typically 16:1 to 30:1. The rotational speed of theextruder may be from 100 to 200 r.p.m.

The toughened thermoplastics of the present invention may, if desired,be further compounded with typical fillers, adjuvents, release agents,antioxidants, antistatic agents, pigments and the like. The amounts anduse of such agents in plastic compounds is well known to those skilledin the art. Additionally, the toughened thermoplastics may be compoundedwith up to 100 parts by weight, per 100 parts by weight offunctionalized polystyrene or polyolefin, of a compatible thermoplasticsuch as polystyrene or a polyolefin, respectively. In some cases theblends of the present invention may have dark colours which may belightened by incorporating an antioxidant.

The present invention will be illustrated by the following examples inwhich parts are by weight (e.g. grams), and temperatures are in °C.

EXAMPLE 1

A phenyl ether tertiary amine was prepared as follows. One equivalent ofdiethanol amine (105 g) was dissolved in isopropanol and the mixture washeated to reflux (88° C.). Drop wise, one equivalent of phenyl glycidylether (150 g) was added to the refluxing mixture. After the completionof the addition of the phenyl glycidyl ether the reaction mixture wasrefluxed for two hours at 88° C. Upon completion of the reaction thesolvent was removed by heating under vacuum. The resulting product isbelieved to have the following structure. ##STR3## For convenience theproduct will be referred to as Q1.

EXAMPLE 2

A series of toughened polystyrene based materials were prepared. Thefollowing procedure was used. A sample of styrene maleic anhydridecopolymer containing about 10 weight percent maleic anhydride sold underthe trademark DYLARK was introduced into the mixing chamber of a Haakemixer. The mixing chamber was at a temperature of 200° C. The DYLARK wasmixed for 30 seconds at 50 rpm. A specified amount of bromobutyl rubberhaving about 2.1% bromination and the tertiary amine were thenintroduced into the mixing chamber and mixed for 3 minutes. Theresulting product was then removed and compression molded at 200° C.into test samples. The IZOD impact of the samples was determined usingASTM procedure D-256.

The tertiary amines used were Q1 from Example 1 and dimethylaminoethanolhereinafter DMAE. The amounts of bromobutyl rubber and tertiary amineand the results of the test are set forth in Table 1.

                  TABLE 1                                                         ______________________________________                                                    Control                                                                              Control                                                                A      B        1        2                                        ______________________________________                                        Styrene maleic                                                                              40       40       40     40                                     anhydride copolymer                                                           Bromobutyl rubber                                                                           0        10       10     10                                     Amine                                                                         Type                            DMAE   Q1                                     Amount        0         0         0.2    0.5                                  Notched IZOD    0.4      0.3      1.0    1.0                                  Ft. lb./ins.                                                                  ______________________________________                                    

The results of Table 1 show about a 2.5 fold increase in notched IZODimpact for samples prepared in accordance with the present inventionover the controls.

EXAMPLE 3

Bromobutyl rubber was mixed with polypropylene grafted with maleicanhydride (sold by Hercules as PC 072) under conditions as in Example 2.In some of the samples 0.5 g of an antioxidant (Irganox 1010) was alsoincorporated into the sample. The product was molded and tested as inExample 2. The results are set forth in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                Control                                                                            Control                                                                  A    B    1    2  3    4                                          __________________________________________________________________________    Grafted Polypropylene                                                                     50   40   40   40 45   30                                         Bromobutyl  0    10   10   10 5    20                                         Amine                                                                         Type        --   --   DMAE Q1 DMAE DMAE                                       Amount      0     0   0.2  0.5                                                                              0.1    0.2                                      Notched IZOD                                                                                0.2                                                                                0.5                                                                              0.7  1.0                                                                              0.5     8.1*                                    without                                                                       antioxidant                                                                   Notched IZOD                                                                                0.2                                                                                0.6                                                                              1.2  1.0                                                                              --   --                                         with antioxidant                                                              Color - without                                                                           W    DB   DB   Y  PY   B                                          antioxidant                                                                   Color - with                                                                              W    B    PY   Y  --   --                                         antioxidant                                                                   __________________________________________________________________________     *Did not break.                                                               W = White                                                                     B = Brown                                                                     DB = Dark Brown                                                               Y = Yellow                                                                    PY = Pale Yellow                                                         

Run 3 shows that there should be not less than about 20 parts of butylrubber per 100 parts of thermoplastic. Run 1 shows that the amine shouldbe present in an amount of at least 0.5 parts by weight per 100 parts byweight of thermoplastic.

EXAMPLE 4

A master batch was prepared by mixing 50 g. of bromobutyl rubber, 1.2 g,of DMAE and 0.5 g. of antioxidant of Example 3 using a Haake mixer at70° C. for 5 minutes at 70 rpm. 10 g. of the resulting master batch wasmixed with 40 g. of styrene maleic anhydride copolymer containing about10 weight percent maleic anhydride (DYLARK 238) and 0.4 g. ofantioxidant of Example 3 using a Haake mixer at 200° C. for 6 minutes at70 rpm. The resulting product was tested in accordance with Examples 2and 3. The notched IZOD impact was 0.83 ft./lb./inch. The molded sampleswere a pale beige. The control values are shown in Table 1.

We claim:
 1. A masterbatch consisting essentially of 20 to 80 parts byweight a copolymer of isoprene and isobutylene in a molar ratio of 1:99to 3:97, which polymer has been halogenated with from 0.5 to 3 weightpercent of chlorine or bromine; and from 0.5 to 1.5 parts by weight ofone or more compatibilizing agents of the formula: ##STR4## wherein R₁and R₂ are C₁₋₄ alkyl or hydroxy alkyl radicals; R₃ is a C₂₋₁₀ alkanolradical or a C₄₋₁₀ hydroxy alkenyl radical provided the double bond isnot adjacent the nitrogen atom or the hydroxyl group; R₄ is a C₆₋₁₀aromatic radical; and n is 0 or 1.